This invention relates to the synthesis and use of urethane foams in grower applications. More particularly, this invention relates to a hydrophilic urethane and a composite urethane foam composition which may incorporate materials such as peat, ground scrap foam, or other filler materials.
In the area of horticulture, it is known to use individual containers for the promotion of seed germination and seedling growth. Seeds may be germinated in small individual containers or subdivided trays containing earth, peat, vermiculite, or other potting material, and grown under controlled greenhouse conditions for quick initial growth. Seedlings are typically transplanted to larger containers or to the field on reaching a sufficient stage of maturity. The filling of such seedling containers with potting material can be a time consuming process, making use of such containers relatively expensive and less desirable than direct planting in the field in some cases. The use of such materials, while providing for robust initial plant growth for seedlings, presents other disadvantages when the seedling is transplanted, either to a larger container or to the field. When a seedling is transplanted, damage to the root system may occur, for example, if the loose potting material falls away from the roots and pulls some of the roots away from the seedling. Root damage occurring during transplantation is a particular problem when seedlings are mechanically transplanted.
The use of a cohesive potting material in such applications has been attempted to alleviate such disadvantages. One previous method used a polyurethane foam as a substrate for plant growth. While the use of polyurethane decreased the likelihood of damage to the root system of seedlings grown in such a medium, polyurethane alone cannot deliver necessary nutrients to the seedling. While some nutrients can be incorporated into a polyurethane foam, others may impair the structural properties of the foam.
Another previous invention overcame some of the disadvantages of both the use of non-cohesive growing material and polyurethane foam plant growth medium by combining foam flakes and nutritives with a binding agent such as polyurethane. This invention provided good hydration to the growing plants due to the water capacity of the foam flakes. The structure of this material also provided for good aeration of the root system of seedlings planted in the material. According to this previous invention, the medium is introduced into a container and subjected to pressure to induce reaction of the polyurethane. This reaction may be accelerated by exposing the composition to steam. Such treatment suffers from the disadvantage that steam treatment sterilizes the medium of microbes, at least some of which may be beneficial for plant growth. If the presence of such microbes is desired, they must be separately added to the medium after the binder has set.
Another known method of making a composite plant growth medium also utilized a pre-polymer such as polyurethane to form a soil composite material. According to this method, a slurry of soil material and water is brought into contact with a water-reactive pre-polymer, initiating a reaction between the pre-polymer and the water. During this initial reaction time, the mixture swells. The mixture is quickly dispensed into receptacles during this initial reaction time. Once deposited in the receptacles, the composite may also be compressed in order for the finished material to assume a predetermined shape or configuration.
A related method includes the mixing of a urethane prepolymer with aggregate material and optionally, fertilizers, herbicides, or related supplements, followed by mixing with sufficient water to form a pourable slurry. The formation of a slurry was previously necessary to insure adequate mixing of the prepolymer and aggregate with water. The pourable slurry is then deposited in a mold to form a shaped aggregate. According to this invention, polyisocyanates are used as the prepolymer, with tolylene diisocyanate being especially preferred. Both this method and the previous method depend on the formation of a pourable slurry of prepolymer, aggregate material, and optionally, surfactant. This dependence on formation of a slurry, however, creates disadvantages in this and similar methods. Namely, foam composites formed from a slurry have a water content which can allow the growth of molds or other microbes which may be harmful to the growing plant or to the structural soundness of the composite, or may simply be esthetically unpleasant to consumers.
Also, foam composites having a significant water content will naturally be heavier than similar products without a high water content, creating greater cost and difficulty in manufacturing and shipping. Furthermore, the use of tolylene diisocyanate can be problematic for individuals who are sensitive to this compound. Previous polyurethane foam compositions also suffered from the disadvantage that these polyurethanes were not hydrophilic, necessitating the addition of wetting agents to permit adequate water penetration into the foam composite.
Therefore, there is a need for a hydrophilic polyurethane composition. There is also a need for a composite foam composition for plant growing applications which may incorporate filler materials such as peat, ground scrap foam, or other filler materials, and is not formed from a prepolymer slurry containing water and filler material.
There is also a need for a method of making a composite foam composition for plant growing applications which may include filler materials such as peat, ground scrap foam, or other filler materials, and which does not include the formation of a prepolymer slurry containing water and filler material.
There is likewise a need for a method of growing a plant in a composite foam composition which is not formed from a prepolymer slurry containing water and filler material.
It is, therefore, an aspect of the present invention to provide a hydrophilic polyurethane foam.
It is another aspect of the present invention to provide a composite foam composition for plant growing applications which may incorporate filler materials such as peat, ground scrap foam, or other materials, and is not formed from a prepolymer slurry containing water and aggregate material.
It is yet another aspect of the present invention to provide a method of making a composite foam composition for plant growing applications which may include filler materials such as peat, ground scrap foam, or other filler materials, and which does not include the formation of a prepolymer slurry containing water and filler material.
It is still another aspect of the present invention to provide a method of growing a plant in a composite foam composition which is not formed from a prepolymer slurry containing water and filler material.
In general, the present invention provides a horticultural growing medium comprising a polyisocyanate-polyol-based polymer, and at least one filler material. The filler material may be any of a variety of additives, such as, for example, earth, sand, peat moss, limestone, gypsum, coir (coconut fiber), and ground floral foam and mixtures thereof. It is also envisioned that other types of foam may be used as filler. Other substances may also be used as filler material, provided that they do not harm growing plants.
The present invention also provides a method, of making a horticultural growing medium comprising the steps of mixing at least one filler material with a polyisocyanate-polyol-based quasi-prepolymer, to form a quasi-prepolymer/filler mixture and applying water to the quasi-prepolymer/filler mixture to form a hydrophilic growing medium. The growing medium may be placed in containers such as trays or other molds and then allowed to solidify into a coherent aggregate. Alternatively, the quasi-prepolymer/filler mixture may be placed into a container prior to being contacted with water. Water may be sprayed onto the quasi-prepolymer/filler mixture in the mold or, the quasi-prepolymer/filler mixture and mold may be immersed in water to cause the quasi-prepolymer to react and foam in the container.
The present invention also provides a method of growing plant seedlings comprising planting a seed or seedling in a horticultural growing medium containing a hydrophilic polyisocyanate-polyol-based polymer and at least one filler material.
The present invention also provides a hydrophilic urethane polymer comprising the reaction product of a quasi-prepolymer and water wherein the quasi-prepolymer contains an isocyanate and a hydrophilic polyol.
Finally, a method of making a hydrophilic polyurethane comprises the steps of adding a hydrophilic polyol to an isocyanate; mixing the polyol and isocyanate to form a quasi-prepolymer, and contacting the quasi-prepolymer with water is provided.
The horticultural growing medium of the present invention displays flexibility, strength, and wetting characteristics which make it an ideal medium for plant growth. Furthermore, the growing medium is formed by a novel method which does not depend on the formation of a slurry, simplifying the pouring of the quasi-prepolymer/filler mixture into molds to form growing medium plugs. The decreased use of water in forming the growing medium plugs decreases the weight of the finished growing medium plugs, thereby decreasing the cost of transporting the finished product to consumers. The decreased water content also improves the ease with which the product can be handled while decreasing the likelihood of the growing medium plugs being subject to rot or other spoilation.
At least one or more of the foregoing aspects, together with the advantages thereof over the known art relating to polyurethane-based growing medium, which shall become apparent from the specification which follows, are accomplished by the invention as hereinafter described and claimed.